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[
J Immunol,
1986]
The development of immunologic methods to reduce transmission of human lymphatic filariasis depends on measures that will enhance the host's ability to eliminate infective larvae, adult worms, or blood-borne microfilariae (mf). The present study was designed to assess the capacity of a crude extract of Brugia malayi mf to decrease the level of microfilaremia and adult worm burden in jirds inoculated with infective larvae, and to identify the filarial antigens that elicit antibody responses in these animals. Thirty weeks after subcutaneous inoculation with 75 infective larvae, 100% of control jirds were patent (i.e., had microfilaremia) compared with 60% of the group immunized with 10 micrograms of crude microfilarial extract (p less than 0.05). In addition, microfilaremia was lower in patent immunized animals compared with controls (p less than 0.05). The mean total number of adult female B. malayi per jird recovered at necropsy in control animals was 16.0 vs 7.0 in immunized jirds (p less than 0.05). Serum of immunized jirds contained anti-mf antibodies with an end titer of 1:8000, a value similar to that of animals with chronic B. malayi infection. Microfilarial antigens of Mr approximately 150,000, 75,000, 42,000, and 25,000 were identified in immunoblotting studies by reactivity with antibodies in sera of immunized jirds. Antibodies induced by immunization with microfilarial extract were not specific for this stage of the parasite life cycle, as jird anti-mf antibodies reacted with a Mr approximately 150,000 and several Mr 50,000 to 110,000 antigens derived from immature and mature adult parasites of both sexes. These data indicate that immunization of jirds with a water soluble microfilarial extract enhances the host's ability to eliminate adult worms and blood-borne mf. The filarial antigens that induce antibodies in immunized jirds have been identified.
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[
J Immunol,
1990]
Immunization of mice with irradiated Brugia larvae or parasite extracts has been shown to induce partial resistance to microfilaremia and enhance clearance of infective larvae. We recently reported the cloning of a 548 amino acid 62-kDa Brugia malayi Ag identified on the basis of reactivity with antisera to a subset of protective microfilarial Ag. Our study describes the protective efficacy against microfilaremia in mice, immunogenicity, and parasite stage-specificity of this candidate vaccine molecule. Immunization of Swiss or BALB/c mice with 1 to 3 micrograms of a 92-kDa trpE fusion protein encoding amino acids 1-479 reduced the intensity of microfilaremia by 40 to 60% compared to control animals given buffer or bacterial trpE (p less than 0.01 to 0.001). Mice immunized with the 92-kDa fusion protein developed delayed-type hypersensitivity reactivity to B. malayi as assessed by enhanced footpad swelling 24 and 48 h after intradermal injection of adult worm extract and in vitro lymph node mononuclear cell proliferation (3H-thymidine uptake) in response to the fusion protein (mean +/- SD stimulation index 4.7 +/- 0.8 vs 2.0 +/- 1.4 for trpE, p less than 0.05). Proliferative responses of lymph node cells coincubated with three other fusion proteins corresponding to the filarial protein truncated from its carboxyl-terminus suggest that dominant T cell epitopes of the 62-kDa Ag are encompassed by amino acids 437-479. Rabbit antibody to the 92-kDa trpE fusion protein immunoprecipitated a 62-kDa polypeptide from [35S] methionine biosynthetically labeled B. malayi microfilariae, adult female, and adult male worms. These data indicate that a recombinant Ag expressed in several developmental stages of B. malayi is capable of inducing partial resistance against microfilariae and Ag-specific T cell responses in mice.
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[
Am J Trop Med Hyg,
1990]
Tropical pulmonary eosinophilia (TPE) is believed to result from extreme immediate hypersensitivity to microfilariae localized in the pulmonary vasculature of some persons with lymphatic filariasis. Female BALB/c mice repeatedly immunized by ip injection of Brugia malayi microfilariae become amicrofilaremic within 24 hr of iv parasite challenge, whereas non-sensitized control animals remain patent for greater than 72 hr. Immunized, but not control mice, develop peripheral blood and pulmonary eosinophilia (2,000 cells/mm3 and 65,000 cells/bronchoalveolar lavage, respectively). Serum and bronchoalveolar lavage filarial-specific IgG antibodies are greater in sensitized mice than in controls (ELISA absorbance values 20- and 10-fold higher, respectively). Serum IgE antibody levels are also greater (P less than 0.01) in immunized parasite-challenged mice than in controls (mean cpm 125I-labeled anti-mouse IgE bound to B. malayi antigen-coated Sepharose beads: 7,852 vs. 1,741, respectively). This model exhibits several of the major features of human TPE: amicrofilaremia, elevated levels of serum IgG and IgE antibodies to microfilariae, and blood and pulmonary eosinophilia. This model may be useful in the examination of the role of filarial antigen-specific lymphoid cells and antibodies in regulating the pathologic responses to microfilariae trapped in the lung.
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[
Mol Biochem Parasitol,
1991]
Diethylcarbamazine (DEC) rapidly lowers the number of microfilariae in the peripheral circulation. The mechanism of action is unknown, but may involve alterations of arachidonic acid metabolism in vascular tissues. We studied the effects of DEC on arachidonic acid metabolism by bovine pulmonary arterial endothelium monolayers, human platelets and Brugia malayi microfilariae. DEC at a concentration of 2.5 microM, a level achieved in vivo, rapidly decreased prostacyclin, prostaglandin E2 and thromboxane B2 release from endothelial monolayers by 78% (P less than 0.001), 57% (P = 0.05), and 75% (P less than 0.05), respectively. High-pressure liquid chromatography of extracts of endothelial monolayers incubated with DEC showed similar inhibition of these cyclooxygenase pathway products, but exposure to the drug did not result in formation of new eicosanoids. DEC did not inhibit endothelial phospholipase A2-dependent release of arachidonate from membrane stores, whereas prostaglandin H2 synthase activity (cyclooxygenae, EC 1.14.99.1) was reduced to a degree similar to that effected by acetylsalicylic acid. Microfilarial but not platelet synthesis of cyclooxygenase products was also reduced by DEC. These data suggest that the mechanism by which DEC lowers the level of microfilariae in the circulation may in part involve its effects on host endothelial and parasite eicosanoid production.
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J Lab Clin Med,
1991]
In human filariasis, large numbers of blood-borne microfilariae circulate unimpeded through the blood stream. How intravascular filarial parasites avoid precipitating thrombosis has not been studied in detail. We hypothesized that extracts of Brugia malayi microfilariae would contain factors that inhibit activation of hemostatic mechanisms. Initial studies demonstrated an inhibitor specific for the intrinsic coagulation cascade. The addition of microfilarial extracts to human plasma prolonged the activated partial thromboplastin time in a dose-dependent fashion but did not prolong the prothrombin, thrombin, or Russell's viper venom times. Microfilarial extracts (0.1 mg/ml) completely inhibited activation of Hageman factor (factor XII, at 0.05 U/ml) as measured in an amidolytic assay. Hageman factor previously activated by ellagic acid (factor XIIa) retained full enzymatic activity in the presence of microfilarial extract (0.1 mg/ml). The presence of inhibitory activity in the culture medium of live parasites raises the possibility that microfilariae secrete an inhibitory protein into their local environment. Microfilarial extracts at a final concentration of 0.1 mg/ml also inhibited collagen- and adenosine diphosphate-induced platelet aggregation. Arachidonic acid-induced platelet aggregation was inhibited by microfilarial extracts at a final concentration of 0.6 mg/ml. These results suggest that microfilariae of Brugia malayi, a human filarial parasite, may avoid initiating thrombosis through inhibition of the intrinsic coagulation pathway and platelet aggregation.
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[
Parasite Immunol,
1998]
Tropical Pulmonary Eosinophilia (TPE) is a severe form of allergic asthma caused by the host inflammatory response to filarial helminths in the lung microvasculature, and is characterized by pulmonary eosinophilia, increased filarial-specific IgG and IgE antibodies, and airway hyperresponsiveness. The current study examined the effect of IL-12 on pulmonary eosinophilia, deposition of eosinophil major basic protein and airway hyperresponsiveness in mice inoculated i.v. with Brugia malayi microfilariae. Injection of recombinant murine IL-12 modulated the T helper (Th) response in the lungs from Th2- to Th1-like, with elevated IFN-gamma, and decreased IL-4 and IL-5 production. Consistent with this shift in cytokine response, antigen-specific IgG2a was elevated, and IgG1 and total serum IgE were decreased. In addition, eosinophils in BAL fluid from IL-12 treated mice were reduced from 56% to 11%, and there was no detectable MBP on respiratory epithelial cells. Importantly, IL-12 suppressed airway hyperresponsiveness compared with saline-injected control animals. Taken together, these data clearly demonstrate that by modulating Th associated cytokine production, IL-12 down-regulates filaria-induced lung immunopathology.
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Proc Natl Acad Sci U S A,
1988]
To facilitate biochemical studies of protective filarial antigens, a lambda
gt11 cDNA library was constructed from Brugia malayi adult mRNA and screened with rabbit sera that recognizes a limited set of filarial antigens of approximately 25, 42, 60, and 112 kDa. Antigens of approximately equal to 25 and approximately equal to 60 kDa have been shown previously to induce enhanced clearance of microfilaremia in mice. A 154-base pair clone detected by immunological reactivity was used to isolate by hybridization a nearly full-length cDNA clone of 1.8 kilobases. Nucleotide-sequence analysis indicated that this clone was derived from a mRNA encoding a 63-kDa antigen. A fusion polypeptide containing 37 kDa of the Escherichia coli TrpE protein (anthranilate synthase) and 55 kDa of the cloned protein was recognized in immunoblot experiments with antisera raised against a partially purified preparation of the approximately equal to 60-kDa protective filarial antigen. These data relate the cloned antigen to a potentially protective antigen in lymphatic filariasis.
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[
Invest Ophthalmol Vis Sci,
1998]
PURPOSE: Intrastromal injection of mice with antigens from the parasitic helminth that causes river blindness (Onchocerca volvulus) induces eosinophil recruitment to the corneal stroma at the time of maximum corneal opacification and neovascularization. The present study was conducted to examine the role of eosinophils and neutrophils in onchocercal keratitis in control C57Bl/6 mice and in interleukin-5 gene knockout (IL-5(-/-)) mice. METHODS: C57Bl/6 and IL-5(-/-) mice were immunized subcutaneously and injected intrastromally with soluble O. volvulus antigens. Mice were killed at various times thereafter. Development of keratitis was assessed by slit lamp examination, and inflammatory cells in the cornea were identified by immunohistochemistry. RESULTS: A biphasic recruitment of inflammatory cells was observed in C57Bl/6 mice; neutrophils predominated during the first 72 hours after intrastromal injection and subsequently declined, whereas eosinophil recruitment increased as time elapsed and comprised the majority (90%) of cells in the cornea by day 7. In contrast, neutrophils were the predominant inflammatory cells in IL-5(-/-) mice at early and late time points and were associated with extensive stromal damage and corneal opacification and neovascularization. Eosinophils were not detected in these mice at any time. CONCLUSIONS: In the absence of eosinophils, neutrophils can mediate keratitis induced by helminth antigens. Together with the early neutrophilic infiltrate in control animals, these observations indicate that neutrophils have an important role in onchocercal keratitis.
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J Immunol,
2007]
The discovery that endosymbiotic Wolbachia bacteria play an important role in the pathophysiology of diseases caused by filarial nematodes, including lymphatic filariasis and onchocerciasis (river blindness) has transformed our approach to these disabling diseases. Because these parasites infect hundreds of millions of individuals worldwide, understanding host factors involved in the pathogenesis of filarial-induced diseases is paramount. However, the role of early innate responses to filarial and Wolbachia ligands in the development of filarial diseases has not been fully elucidated. To determine the role of TLRs, we used cell lines transfected with human TLRs and macrophages from TLR and adaptor molecule-deficient mice and evaluated macrophage recruitment in vivo. Extracts of Brugia malayi and Onchocerca volvulus, which contain Wolbachia, directly stimulated human embryonic kidney cells expressing TLR2, but not TLR3 or TLR4. Wolbachia containing filarial extracts stimulated cytokine production in macrophages from C57BL/6 and TLR4(-/-) mice, but not from TLR2(-/-) or TLR6(-/-) mice. Similarly, macrophages from mice deficient in adaptor molecules Toll/IL-1R domain-containing adaptor-inducing IFN-beta and Toll/IL-1R domain-containing adaptor-inducing IFN-beta-related adaptor molecule produced equivalent cytokines as wild-type cells, whereas responses were absent in macrophages from MyD88(-/-) and Toll/IL-1R domain-containing adaptor protein (TIRAP)/MyD88 adaptor-like (Mal) deficient mice. Isolated Wolbachia bacteria demonstrated similar TLR and adaptor molecule requirements. In vivo, macrophage migration to the cornea in response to filarial extracts containing Wolbachia was dependent on TLR2 but not TLR4. These results establish that the innate inflammatory pathways activated by endosymbiotic Wolbachia in B. malayi and O. volvulus filaria are dependent on TLR2-TLR6 interactions and are mediated by adaptor molecules MyD88 and TIRAP/Mal.
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Ricchiuto A, Konadu P, Debrah AY, Gruetzmacher B, Weil G, Kazura JW, Klarmann-Schulz U, Dubben B, Hoerauf A, Nadal J, Mubarik Y, King CL, Batsa Debrah L, Osei-Mensah J, Fimmers R, Ayisi-Boateng NK, Fischer K
[
Clin Infect Dis,
2019]
BACKGROUND: Improved treatment for onchocerciasis is needed to accelerate onchocerciasis elimination in Africa. Aiming to better exploit registered drugs, this study was undertaken to determine whether annual or semiannual treatment with ivermectin (IVM; 200g/kg) plus albendazole (ALB; 800mg single dose) is superior to IVM alone. METHODS: This trial was performed in Ghana and included 272 microfilaria (MF) -positive participants randomized to 4 treatment arms: 1) IVM annual at 0, 12, and 24 months; 2) IVM semiannual at 0, 6, 12, 18 and 24 months; 3) IVM+ALB annual; 4) IVM+ALB semiannual. Microfiladermia was determined pre-treatment and at 6, 18 and 36 months. The primary outcome was the proportion of fertile and viable female worms in onchocercomata excised at 36 months. RESULTS: Post-treatment nodule histology showed that 15/135 (11.1%), 22/155 (14.2%), 35/154 (22.7%) and 20/125 (16.0%) living female worms had normal embryogenesis in the IVM annual, IVM semiannual, IVM+ALB annual and IVM+ALB semiannual groups respectively (p=0.1229). Proportions of dead worms also did not differ between the 4 groups (p=0.9198). Proportions of patients without MF at 36 months (one year after the last treatment) were 35/56 (63%) after annual IVM, 42/59 (71%) after semiannual IVM, 39/64 (61%) after IVM+ALB annual, and 43/53 (81%) after semiannual IVM+ALB. CONCLUSIONS: The combination treatment with IVM plus ALB was no better than IVM alone for sterilizing, killing of adult worms or achieving sustained MF clearance. However, semiannual treatment was superior to annual treatment for achieving sustained clearance of O. volvulus MF from the skin (p=0.024).